Red eye reduction

If you've ever taken a photo in low light using a compact camera or an SLR with built-in flash you will have no doubt come across a strange effect - people with alien-looking eyes. The reason is simple; the flash lights up all the blood vessels in the eye which reflect back into the lens. The further away the flash is from the lens the less likely the chances of this strange phenomena occurring. The problem with built-in flash is that you can't control where the flash fires from. To overcome this, many cameras have a red-eye reduction mode, but it is, as the name suggests, only a reducer. It works by firing a pre flash to reduce the size of the pupils, and in doing so reduces the area of red. The redness is still usually apparent, but because the pupil is smaller the effect is less noticeable. There are three methods used in cameras to reduce red-eye. One is a single pre flash. This is quite bright and can fool the subject into thinking the picture has been taken. So you avoid red-eye but have a picture of a person either looking away or blinking. The second method fires a less powerful, but equally distracting, sequence of flashes, almost like a strobe. This can result in the unaware person shielding their eyes from the potential epilepsy inducing strobe! Version three tends to be the most subtle - a torch-like light that shines for about five seconds before the flash is taken. The only downside of this is battery drain. If you have a computer you can remove red-eye digitally using image editing software. If you don't there are special pens available that you can use to colour in the red on your photos.

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